Method and apparatus for processing pel signals of an image

Abstract

A system for processing image data of a text document in compressed form wherein pel signals of the original image are stored in pel positions in an input image buffer and the pel signals stored in every other pel (EOP) positions in the input buffer are sequentially fetched, along with respective pluralities of neighboring pel signals stored in EOP positions and compressed by adaptive arithmetic compression to generate a first set of compressed data which is stored in a memory. The pel signals stored in remaining pel (RP) positions in the input image buffer are also sequentially fetched, along with respective pluralities of neighboring pel signals, including at least one signal stored in an RP position and a plurality of signals stored in EOP positions, and compressed by adaptive arithmetic compression to generate a second set of compressed data which is stored in a memory. The first and second sets of compressed data may be decompressed to reproduce the pel signals stored at EOP positions, and the pel signals stored in RP positions along with their respective pluralities of neighboring pel signals stored in EOP positions, and stored in an output image buffer. The fetching operation includes selecting one of a plurality of sampling windows, each having a different sampling pattern, for sampling the pel signals making up the first and second sets of data during compression and decompression to achieve the improved data volumes.

We claim: 
     
       1. An apparatus for processing pel signals representing the pels of an original image comprising: input image buffer means for storing pel signals representing said original image in pel positions therein;   compression means for generating a first set of compressed data representing pel signals stored in every other pel (EOP) positions in said input image buffer means, and for generating a second set of compressed data representing pel signals stored in remaining pel (RP) positions and associated EOP positions in said input image buffer;   memory means for storing said first set of compressed data and said second set of compressed data;   decompression means for decompressing said first set of compressed data to reproduce said EOP pel signals, and for decompressing said second set of compressed data to reproduce said RP and associated EOP pel signals;   output image buffer means for storing said reproduced EOP pel signals in every other pel positions therein and said reproduced RP pel signals in remaining pel positions therein; and wherein   said compression means comprises first sampling means for sequentially sampling each pel signal stored in said EOP positions in said input image buffer along with a plurality of neighboring pel signals in said EOP positions, during the generation of said first set of compressed data, and, second sampling means for sequentially sampling each pel signal stored in said RP positions along with a plurality of neighboring pel signals, including at least one pel signal in another RP position and a plurality of pel signals in said EOP positions, during the generation of said second set of compressed data; and   said first sampling means comprises a window means having a sampling pattern, for sampling, as a current pel signal, each pel signal stored in said EOP positions in said input image buffer, and also sampling a plurality of neighboring pel signals in said EOP positions, selected in accordance with the pel position of said current pel signal, when generating said first set of compressed data.   
     
     
       2. An apparatus according to claim 1, wherein said original image is a text image, said data compression means comprises means for performing adaptive arithmetic compression, and said data decompression means comprises means for performing adaptive arithmetic decompression. 
     
     
       3. An apparatus for processing pel signals representing the pels of an original image comprising: input image buffer means for storing pel signals representing said original image in pel positions therein;   compression means for generating a first set of compressed data representing pel signals stored in every other pel (EOP) positions in said input image buffer means, and for generating a second set of compressed data representing pel signals stored in remaining pel (RP) positions and associated EOP positions in said input image buffer;   memory means for storing said first set of compressed data and said second set of compressed data;   decompression means for decompressing said first set of compressed data to reproduce said EOP pel signals, and for decompressing said second set of compressed data to reproduce said RP and associated EOP pel signals;   output image buffer means for storing said reproduced EOP pel signals in every other pel positions therein and said reproduced RP pel signals in remaining pel positions therein; and wherein   said compression means comprises first sampling means for sequentially sampling each pel signal stored in said EOP positions in said input image buffer along with a plurality of neighboring pel signals in said EOP positions, during the generation of said first set of compressed data, and, second sampling means for sequentially sampling each pel signal stored in said RP positions along with a plurality of neighboring pel signals, including at least one pel signal in another RP position and a plurality of pel signals in said EOP positions, during the generation of said second set of compressed data; and   wherein said second sampling means comprises a plurality of sampling window means, each having a different sampling pattern, for sampling, as a current pel signal, each pel signal stored in said RP positions in said input image buffer and also sampling a plurality of neighboring pel signals, selected in accordance with the pel position of said current pel signal, when generating said second set of compressed data.   
     
     
       4. An apparatus as in claim 3, wherein said pel positions comprise vertical and horizontal lines in said input image buffer and said plurality of window means comprise: first window means for sampling a pel signal stored in one of said RP positions in a horizontal line containing EOP positions, as a current pel signal and the two horizontally adjacent pel positions stored in the EOP positions in the pel line containing said current pel signal along with the pel signal stored in the RP position in the preceding pel line positioned above said current pel signal, and the two pel signals stored in EOP positions in the next but one pel line positioned below said two horizontally adjacent pel signals, respectively.   
     
     
       5. An apparatus as in claim 3, wherein said pel positions comprise vertical and horizontal lines in said input image buffer and said plurality of window means comprise: second window means for sampling a pel signal stored in one of said RP positions in a vertical line containing EOP positions, as a current pel signal, and the two vertically adjacent pel signals stored in the EOP positions in preceding and next pel lines, respectively, to the pel line containing said current pel signal, along with the pel signal stored in the left adjacent RP pel position in the horizontal line of said current pel signal, and the two pel signals stored in said preceding and next pel lines positioned in the next but one pel positions of said two vertically adjacent pel signals, respectively.   
     
     
       6. An apparatus as in claim 3, wherein said pel positions comprise vertical and horizontal lines in said input image buffer and said plurality of window means comprise: third window means for sampling a pel signal stored in one of said RP positions, as a current pel signal, and the four pel signals stored in the EOP positions centered about said current pel signal in the horizontal preceding and next pel lines to the horizontal line of said current pel signal, along with the pel signal stored in the RP position in said preceding pel line positioned above said current pel signal, and the pel signal stored in the left adjacent RP pel position in the line of said current pel signal.   
     
     
       7. An apparatus according to claim 3, wherein said original image is a text image, said data compression means comprises means for performing adaptive arithmetic compression, and said data decompression means comprises means for performing adaptive arithmetic decompression. 
     
     
       8. A method for processing pel signals of an original image comprising the steps of: (a) providing an input image buffer, an output image buffer, and a memory;   (b) storing pel signals representing said original image in pel positions of said input image buffer;   (c) sequentially fetching the pel signals stored in every other pel (EOP) positions in said input image buffer along with respective pluralities of neighboring pel signals stored in said EOP positions;   (d) compressing said sequentially fetched pel signals along with their respective pluralities of neighboring pel signals to generate a first set of compressed data representing said pel signals stored in said EOP positions;   (e) storing said first set of compressed data in said memory;   (f) sequentially fetching the pel signals stored in remaining pel (RP) positions in said input image buffer along with respective pluralities of neighboring pel signals, including at least one signal stored in an RP position and a plurality of signals stored in said EOP positions;   (g) compressing said sequentially fetched pel signals in said RP positions along with their respective pluralities of neighboring pel signals to generate a second set of compressed data;   (h) storing said second set of compressed data in said memory;   (i) decompressing said first set of compressed data to reproduce said pel signals stored at EOP positions;   (j) storing said reproduced pel signals stored in EOP positions, in EOP positions in said output image buffer;   (k) decompressing said second set of compressed data to reproduce said pel signals stored in RP positions along with their respective pluralities of neighboring pel signals stored in EOP positions; and   (l) storing said reproduced pel signals stored in RP positions and said respective neighboring pel signals stored in EOP positions, respectively in RP and EOP positions of said output image buffer; and wherein said original image is a text image, and said step (c) includes the steps of selecting a window for sampling, as a current pel signal, each of said pel signals stored in said EOP positions, and also sampling said plurality of neighboring pel signals at EOP positions selected in accordance with the pel position of said current pel signal, and moving said window on said input image buffer until all pel signals in said EOP positions have been sampled and fetched as said current pel signal.     
     
     
       9. A method according to claim 8, wherein said compressing in steps (d) and (g) is by adaptive arithmetic compression. 
     
     
       10. A method according to claim 9, wherein said decompressing in steps (i) and (k) is by adaptive arithmetic decompression. 
     
     
       11. A method according to claim 8, wherein said original image is a text image, said compression steps comprise performing adaptive arithmetic compression, and said data decompression steps comprise performing adaptive arithmetic decompression. 
     
     
       12. A method for processing pel signals of an original image comprising steps of: (a) providing an input image buffer, an output image buffer, and a memory;   (b) storing pel signals representing said original image in pel positions of said input image buffer;   (c) sequentially fetching the pel signals stored in every other pel (EOP) positions in said input image buffer along with respective pluralities of neighboring pel signals stored in said EOP positions;   (d) compressing said sequentially fetched pel signals along with their respective pluralities of neighboring pel signals to generate a first set of compressed data representing said pel signals stored in said EOP positions;   (e) storing said first set of compressed data in said memory;   (f) sequentially fetching the pel signals stored in remaining pel (RP) positions in said input image buffer along with respective pluralities of neighboring pel signals, including at least one signal stored in an RP position and a plurality of signals stored in said EOP positions;   (g) compressing said sequentially fetched pel signals in said RP positions along with their respective pluralities of neighboring pel signals to generate a second set of compressed data;   (h) storing said second set of compressed data in said memory;   (i) decompressing said first set of compressed data to reproduce said pel signals stored at EOP positions;   (j) storing said reproduced pel signals stored in EOP positions, in EOP positions in said output image buffer;   (k) decompressing said second set of compressed data to reproduce said pel signals stored in RP positions along with their respective pluralities of neighboring pel signals stored in EOP positions; and   (l) storing said reproduced pel signals stored in RP positions and said respective neighboring pel signals stored in EOP positions, respectively in RP and EOP positions of said output image buffer; and wherein said step (f) includes the step of selecting one of a plurality of sampling windows, each having a different sampling pattern, for sampling, as a current pel signal, each of said pel signals stored in said RP positions in said input image buffer, and also sampling said respective plurality of neighboring pel signals at positions selected in accordance with the pel position of said current pel signal, until all pel signals in said RP positions have been sampled and fetched as said current pel signal.     
     
     
       13. A method as in claim 12, wherein said pel positions comprise vertical and horizontal lines in said input image buffer and said plurality of windows include: a third window for sampling, as a current pel signal, a pel signal stored in an RP position in a horizontal current pel line, and for sampling four pel signals which include EOP positions centered about said current pel signal in the horizontal preceding and next pel lines to the line of said current pel signal, along with one pel signal stored in the RP position in said preceding pel line positioned above said current pel signal, and one pel signal stored in the left adjacent pel position in the line of said current pel signal. 
     
     
       14. A method as in claim 12, wherein said pel positions comprise vertical and horizontal lines in said input image buffer and said plurality of windows include: a first window having a sampling pattern for sampling, as a current pel signal, a pel signal stored in an RP position in a current horizontal pel line containing EOP positions, and for sampling the two horizontally adjacent pel signals stored in the EOP pel positions between which the current pel is interposed in said current pel line; the pel signal stored in the RP position above said current pel signal in the preceding pel line; and the two pel signals stored in EOP positions in the next but one pel line below said two horizontally adjacent pel signals, respectively. 
     
     
       15. A method as in claim 12, wherein said pel positions comprise vertical and horizontal lines in said input image buffer and said plurality of windows include: a second window for sampling, as a current pel signal, a pel signal stored in an RP position in a vertical pel line containing EOP positions, and for sampling the two vertically adjacent pel signals stored in the EOP positions in preceding and next horizontal pel lines, respectively, to the pel line containing said current pel signal, along with the pel signal stored in the left adjacent RP pel position in the horizontal line of said current pel signal, and the two pel signals stored in said preceding and next pel lines positioned in the next but one pel positions of said two vertically adjacent pel signals, respectively. 
     
     
       16. A method according to claim 13, wherein said original image is a text image, said compressing steps comprise performing adaptive arithmetic compression, and said data decompressing steps comprise performing adaptive arithmetic decompression. 
     
     
       17. A method according to claim 13, wherein said compressing in steps (d) and (g) is by adaptive arithmetic compression. 
     
     
       18. A method according to claim 17, wherein said decompressing in steps (i) and (k) is by adaptive arithmetic decompression.